1. Field of the Invention
This invention relates generally to fluid-pressure brake and analogous systems and more particularly to automatic application valves for use therewith.
2. Description of the Prior Art
Presently, air brake systems for towed vehicles generally comprise three arrangements. First, there is the type of system utilizing a single service reservoir for providing a source of pressurized air to all the service brake chambers and a single emergency or parking reservoir for supplying pressurized air to all the parking brake chambers. Second, there is the type of system utilizing more than one service reservoir each providing a source of air for operating some of the service brake chambers and a single parking reservoir for supplying pressurized air to all the parking brake chambers. Third, there is the type of system utilizing plural service reservoir capability to provide at least partial service braking in the event of failure in one of the service systems and also having plural parking reservoir capability, so that, in the event of failure in one or more of the parking reservoirs, there will still be air pressure retained in the parking brake chambers to prevent the undesirable automatic application of the parking brakes.
The third system, described above, includes an air receiving portion, a valve portion, an air storage portion and a brake portion. The valve portion includes a multiplicity of valves interconnected with costly external "plumbing" for cooperative functioning with the other portions of the system. It would therefore be of benefit to have, in conjunction with a service and parking brake system offering more than single service reservoir capability to provide at least partial service braking in the event of failure in one of the service systems and also offering more than single parking reservoir capability so that, in the event of failure in one of the parking reservoirs, there would still be air pressure communication with the parking brake chamber to prevent the undesirable automatic application of the parking brakes, a valve for use in applying brake releasing pressure to the brake chambers which valve includes multiple cooperative functions thus eliminating the need for the costly external plumbing and the multiplicity of various valves generally associated with such systems.